Remotely setting thermostatic switch assembly and refrigeration system employing same

ABSTRACT

A remotely changeable thermostat for a refrigeration or air conditioning system and method and system employing same. The thermostat has a fluid filled capsule with a diaphragm movably responsive to fluid expansion and contraction for actuating, via lever means, a compressor power switch. The capsule senses temperature via a fluid filled capillary. A separate remote user activated switch energizes an electrical actuator for moving the fulcrum of the lever means to change the sensed temperature of the evaporator at which the power switch is actuated. The user activates a remote switch to energize an electrical heater coil for heating a bimetal strip which moves the fulcrum for the lever means between a high or low temperature setting for compressor power switch actuation in response to user opening or closing the remote heater switch.

BACKGROUND OF THE INVENTION

The present invention relates to thermostatic switch assemblies of thetype employing a temperature responsive element operative to effectactuation and deactuation of an electrical switch for controllingcurrent flow to a load circuit.

Thermostatic assemblies of the aforesaid type are often employed forcontrolling current flow to a compressor motor for a stationaryrefrigeration or air conditioning system and in vehicular applicationsto control current flow to the compressor clutch where the clutch isdriven by a power transmission connected to the vehicle engine.

Thermostatic switch assemblies typically employ a temperature responsivemember such as a fluid filled capsule having a movable diaphragm-wallportion or a bimetal element which moves upon experiencing changes inthe sensed temperature. In refrigeration control systems eitherstationary or vehicular, it is desired to sense the temperature of therefrigerant flowing at certain locations in the circuit such as forexample, at the evaporator and to effect cycling of the compressor inresponse to preselected sensed temperatures.

Thermostatic switch assemblies of the aforesaid mechanical type havebeen proven inexpensive to manufacture in high volume and reliable overextended periods of operation in the environments to which refrigerationsystems are subjected.

However, in certain applications such as automotive air conditioningsystems it has been desired to provide for a change of mode of operationin which the compressor clutch is cycled. It has been desired tomaintain the refrigerant in the evaporator at slightly higher values inorder to shorten the compressor duty cycle and effect economy ofoperation of the vehicle, inasmuch as the additional load of thecompressor is applied to the engine for minimum time periods in order toeffect a satisfactory level of passenger compartment comfort. It hasbeen also desired to provide a "Maximum Cool Down" mode of operation fora vehicle air conditioning system and particularly where the vehicle hasbeen sitting in the sun for extended periods of time and the passengercompartment is at intolerable elevated temperature levels upon initialentry of the passengers.

If the temperature settings for the compressor cycling are establishedat values to maintain the evaporator at the lowest permissibletemperature for effecting maximum cooling of the passenger compartment,the compressor will cycle for unnecessarily long periods of time inorder to maintain the evaporator at a minimum temperature for fastestcooling.

Accordingly it has been desired to provide a vehicle air conditioningsystem in which the system could be initially operated for cooling theevaporator to the minimum temperature permissible without causingfreezing and ice formation on the surface of the evaporator, to provideMaximum Cool Down. It has further been desired to enable the system tobe later switched by the user or vehicle operator to a mode of operationwherein a lesser amount of cooling is employed to thereafter maintainthe passenger compartment at a desired comfort level.

However, in the past where mechanical temperature sensing or pressuresensors have been employed at the evaporator to determine refrigeranttemperature, in order to provide a dual mode of operation it has beennecessary to provide separate sensors having different temperaturesettings and to switch between sensors. Therefore, it has been desiredto provide a refrigeration system and particularly an automotive vehicleair conditioning system wherein reliable mechanical temperature sensingmeans are employed for monitoring evaporator temperature to actuate anddeactuate a switch for cycling the electrical compressor drive clutchand to provide remote changing of the cycling temperatures for thecompressor and yet maintain the reliability of the mechanicaltemperature sensing devices.

However, it has not been known how to remotely change the temperaturesetting of a mechanical temperature sensor or thermostat once installedin the system. It has been particularly desired to find a way toremotely control the thermostat when located on the evaporator or on thesuction return line in the engine compartment of the vehicle.

SUMMARY OF THE INVENTION

The present invention provides a unique and novel control system for arefrigeration system and particularly an automotive vehicle airconditioning system wherein a way or means is provided for permittingthe vehicle operator or occupant to remotely change the duty cycle ofthe air conditioning compressor by selecting a relatively high or lowsetting for a thermostat which senses the temperature of the refrigerantcirculating through the evaporator and controls the temperature at whichthe compressor clutch is energized and de-energized.

In a first or "Economy" mode of operation where the primary temperatureis selected the thermostat is mechanically altered by electricallyoperated means switched on or off as may be desired by actuation of thevehicle operator select switch located in the passenger compartment. Inthe first mode the compressor operates to maintain the evaporatortemperature at a first or higher selected level to thereby reduce theoperating time for the compressor and minimize the power drain on thevehicle engine. For given ambient conditions and the "Economy" modeminimizes the portion of the driving time in which the engine is loadedwith the air conditioning compressor; and, thus effects minimum loss offuel economy attributable to operation of the air conditioning system.

The second mode of operation for "Maximum Cool Down" mode enables thevehicle operator to change the mechanical thermostat via a remotelypositioned electrical operator select switch in the passengercompartment to cause a change in the setting of the thermostat whichcontrols the compressor clutch cycling in response to a sensedevaporator temperature. A Maximum Cool Down mode of operation isgenerally desired when the vehicle has been sitting for an extendedperiod of time in the sun.

The present invention employs a mechanically operated temperature sensorpreferably a fluid filled capillary and bulb type but which may alsocomprise a bimetal device for actuating an electric switch in responseto the sensed refrigerant or evaporator temperature reaching apreselected level. Actuation of the electric switch energizes thevehicle refrigerant compressor clutch which operates until theevaporator temperature reaches a preselected level at which point thesensor via a lever means deactuates the switch to de-energize thecompressor clutch.

The lever means employed between the temperature sensor and the electricswitch is fulcrummed on the switch housing. In the preferred form, thepressure sensor comprises a fluid filled pressure capsule having aportion of the wall formed as a diaphragm which acts against one end ofthe lever means for actuating the electric switch.

The lever means is fulcrummed on the switch housing by means of a memberslidably mounted on the switch housing for movement betweenpredetermined limits. An electrically energized actuator is selectivelyoperated by the vehicle operator opening or closing a remote operatorselect switch to provide power to an electrically energized actuator formoving the fulcrum member between its limits. In the preferredembodiment, the electric actuator comprises the bimetal element heatedby an electric coil provided thereon.

The present invention thus employs a mechanically actuated thermostatfor a refrigerant compressor, particularly for a vehicle airconditioning system, which may have the settings of the thermostatvaried by energizing an electrically heated actuator for changing thefulcrum of the lever means between the temperature sensor of thethermostat and the electric load switch. The present invention thuspermits the vehicle operator to select as between a high or lowtemperature setting at which it is desired to energize the vehiclecompressor clutch for either a "Maximum Cool Down" or "Economy" mode ofoperation.

It is an object of the present invention to provide a method and way ormeans of enabling the user to remotely change the sensed refrigeranttemperature at which a compressor is cycled in a refrigeration system.More particularly, it is an object to enable a user to remotely changethe sensed refrigerant temperatures at which a vehicle air conditioningcompressor clutch is cycled for rapid cooling or energy conserving modesof operation. It is another object of the invention to provide amechanically actuated thermostat employing lever means between thetemperature sensor and the load controlling switch with a remotelyenergizable electrical actuator for changing the position of the fulcrumpoint of the lever means for changing the actuation temperature of theload switch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial schematic of a vehicle air conditioning systememploying the present invention;

FIG. 2 is a somewhat perspective view of a portion of the thermostatemployed in the embodiment of FIG. 1;

FIG. 3 is a view taken along view-indicating lines 3--3 of FIG. 2 andshows in further detail the thermostat of FIG. 2,

FIG. 4 is a cross-sectional view of the operating mechanism of thethermostat of FIG. 2 taken along section-indicating lines 4--4.

DETAILED DESCRIPTION

Referring to FIG. 1, a vehicle air conditioning system is indicatedgenerally at 10 employing a compressor 12 driven by a power belt 13connected to the engine crank shaft pulley (not shown) and drivinglyconnected to the compressor 12 by an electrically energized clutch 14.The pressurized refrigerant from compressor 12 is discharged alongconduit 16 through a condenser 18 which is cooled by a suitable fan 17driven by motor 19 receiving power along lead 21 from a controller 23with the other side of the fan motor 19 connected through lead 24 to thesystem ground. Alternatively, as is well known, the fan may be driven bya power belt from the engine shaft.

The condenser discharges through conduit 20 to the inlet of a thermalexpansion means indicated generally at 22 which is typically amechanically operated thermal expansion valve or capillary. The liquidrefrigerant discharges from the expansion means 22 at a lower pressurealong conduit 26 which is connected through the inlet of an evaporatorindicated generally at 28 and disposed for heat transfer relation withthe air in a vehicle passenger compartment.

The vaporized refrigerant from evaporator 28 is discharged along conduit30 which passes through the expansion device 22 and is connected toconduit 32 for return to the compressor suction inlet.

Fan control 23 receives power through an operator activated switchindicated generally at 34 via junction 36 which is also connected vialead 38 to the thermostat indicated generally at 40.

The thermostat has a switch indicated generally at 42 disposed thereinhaving the base of a movable blade 44 connected to the power lead 38.Blade 44 has a contact 46 mounted adjacent the end thereof which closesagainst a stationary contact 48 connected via lead 50 to the powerterminal of clutch 14 with the opposite side of the clutch connected tothe system ground via lead 52. Thus, upon closure of switch 42 thecompressor clutch is energized when the operator switch 34 is closed;and, upon opening of switch 42 the compressor clutch 14 is de-energized.

The movable contact of switch 42 is actuated by a lever means indicatedgenerally at 54 which includes a member 56 having one end contactingmovable switch blade 44 and the other end pivoted about a stationaryfulcrum 58, which is adjustable as will hereinafter be described ingreater detail.

The lever means 54 includes a second lever member 60 which is pivotedabout a second fulcrum indicated generally at 62 which includes aslidable member 64 movable between limits provided by a stop 66. One endof lever 60 contacts the lever arm 56 with an intermediate portion 68thereof contacting a movable diaphragm 70 which forms a wall portion ofa fluid pressure capsule 72 filled with fluid and connected to a sensingcapillary tube 74 which has the end thereof, which may be formed as abulb 76, if desired, disposed at the desired location in the refrigerantcircuit. In the embodiment illustrated in FIG. 1, the sensing bulb 76 isdisposed adjacent the discharge line of the evaporator 28 for sensingthe temperature of the refrigerant in a saturated vapor state which isassumed to be the saturation temperature of the refrigerant. It will beunderstood however that the end of capillary 74, or bulb 76, may bedisposed at other desired locations for temperature sensing as forexample the middle of the evaporator or at the suction return line 32.The particular location of the sensing bulb 76 is determined by theparticular location of the refrigerant circuit which is deemed to becritical insofar as controlling the cycling of the compressor clutch.

In general, warming of bulb 76 causes the fluid therein to expand movingdiaphragm 70 to pivot member 60 about the fulcrum 62 and move lever 56to actuate switch 42 for energizing the compressor. When the compressorhas caused the evaporator to cool the surrounding air such that thetemperature of the evaporator is lowered to the desired level, the fluidin capsule 72 contracts to cause member 60 to pivot in a reversedirection about fulcrum 62 to effect movement of lever 56 in a manner todeactuate switch 42.

The fulcrum 62 is moved by energization of an electrical actuator meansindicated generally at 78 which as hereinafter described in greaterdetail comprises an electrically heated bimetallic element energized byan "operator select" switch 80 which is remote from thermostat 40 and ispowered via lead 82 from junction 85 connected to the line switch 34.

Switch 80 is connected via lead 86 to the electrical actuator 78 whichhas the opposite side thereof connected through lead 88 to the systemground. Power junction 84 is connected to the positive lead of a battery90 with the negative lead of the battery typically connected to thesystem ground via lead 92.

With switch 34 closed, when operator select switch 80 is closed theelectrical actuator 78 is energized to move fulcrum means 62 from afirst to a second position to change the pivot point of the lever 60.Upon opening of the operator select switch 80, the electrical actuator78 is de-energized and the fulcrum means 62 is moved back to a firstposition.

Referring now to FIGS. 2, 3 and 4, the thermostat 40 of the presentinvention is shown in greater detail.

Referring particularly to FIGS. 2 and 3, the fulcrum 62 for the levermeans comprises a sliding member 64 having an elongated slot 65 providedtherein and which is slidably received over a post or peg 66 whichlimits the movement of the member 64 in the vertical direction. Themember 64 has a right angle tab 67 provided at the upper end thereofwhich is contacted by and receives thereagainst the driving or movingforce of the electrical actuator 78. The member 64 is retained over thepost 66 by a suitable retainer such as the pressed-on spring clip 94which is eliminated in FIG. 2 for clarity. The lower end of member 64defines a fulcrum or pivot surface 69 for lever 60.

The electrical heater means 78 comprises an elongated bimetal strip 96received in slots or grooves 98, 100 formed in the side of thethermostat housing 102. The bimetal strip has the ends thereof 104, 106turned upwardly at generally right angles thereto to provide reactionsupport for the bimetal. The central portion of the bimetal strip 96contacts the tab 67 on sliding member 64 generally in the center regionthereof. In the presently preferred practice, tab 67 is welded to strip96. Bimetal strip 96 has a heater coil of resistive conductor materialas for example nichrome wire wrapped around the strip 96; and, the coilis denoted by reference numeral 108 in the drawings. The ends of thecoil 108 are attached to power leads 110, 112 by switchable electricalconnection, preferably weldment, to the ends of the strip which leadsare respectively connected to the leads 86 and 88 for connection in thecircuit.

Electrical lead 112 is connected to a tab on contact strip 113 which isconnected to electrical connector terminal 115 as shown in FIG. 2.Terminal 115 in the system of FIG. 1 is connected to power lead 86.Electrical lead 110 is connected to the metal housing of the capsule 72and to the system ground.

Referring particularly to FIGS. 3 and 4, the lever member 60 has theleft end thereof pivoted about the lower end 69 of the sliding member64. A tab 68 is formed on lever 60 intermediate the ends thereof forcontacting the central region of diaphragm 70 which forms the upperportion of the wall of pressure capsule 72. Capsule 72 is attached tothe housing 102 by suitable expedients such as metal brackets, whichhave been omitted in the drawings for clarity.

The opposite end of the lever member 60 is registered against a secondlever member 56 which has the right hand end thereof in FIG. 4contacting and registered against a stationary pivot 58 comprising thespherical end of an adjustment screw 118 threadably received in thehousing 102 for adjustment during calibration. The left hand end of thelever member 56 is formed to a generally U-shaped configuration asdenoted by reference numeral 57 in FIG. 4.

The member 56 has a separate spring arm associated therewith denoted byreference numeral 120 which is in generally side-by-side relationshiptherewith and which arm 120 has the end thereof spaced from the U-shapedportion 57 of arm 56. It will be understood that arm 120 attached to astationary pivot (not shown) adjacent pivot 58. The member 120 extendsin cantilever from its stationary pivot mount with end 121 thereof free.

Arm 56 is biased downwardly by a spring 122 which has its upper endregistered against housing portion 124 and its lower end registered overa tab 126 provided on the member 56 such that the spring 122 urges thelever member 56 downwardly against the right hand end of member 60.

With continued reference to FIG. 4, a blade spring 44 is anchored at itsleft hand end on a suitable mounting ledge (not shown) provided onhousing 102 and which is connected to a stop member 130 provided at theopposite end of the blade 44. The stop member 130 and the stationary endof blade 44 at mounting tab 128 are both connected to a common strip andto the electrical terminal connector denoted by reference numeral 132 inFIG. 2. Stationary electrical contact 48 is mounted on a stationarycontact strip 133 which is connected to an electrical connector terminaldenoted by reference numeral 135 in FIG. 2.

Referring to FIG. 4, a toggle or yoke member 134 has a generallyC-shaped configuration and has a notch 136 formed on the outer surfaceof one side thereof with an edge of blade member 44 near the stationaryend thereof received in the notch such that the member 134 is pivotedthereabout. Member 134 has a second notch 138 provided on the outersurface of the side of the generally C-shaped configuration oppositenotch 136; and, the second notch 138 has received therein one end of anarcuately shaped beam spring 140 which has its opposite end secured tothe end of blade member 44. Beam spring 140 thus biases the notch 136 ofthe toggle member into contact with the stationary end of blade member44. One end of the C-shaped toggle member 134 has a rounded stop surface142 provided thereon which is disposed between the U-shaped end 57 oflever arm 56 and the end of spring arm 120 which thus form limit stopsfor movement of the toggle member 134.

In operation, as the capillary tube end or bulb 76 senses an increasetemperature, fluid within the capillary 74 and capsule 72 expands tocause diaphragm 70 to move upward thereby moving contact tab 68 upwardand pivoting lever arm 60 about the fulcrum surface 69.

The right hand end of lever arm 60 moves lever arm 56 about stationarypivot 58 causing the U-shaped leg of arm 56 to move upward.

The right hand end of arm 56 also contacts arm 120 moving it upwardcausing the free end 121 thereof to contact surface portion 142 of yoke134 pivoting the yoke 134 counterclockwise about the stationary blade atnotch 136. As the yoke member 134 pivots counterclockwise and movesnotch 138 and the beam spring 140 upwardly, beam spring 140 goes throughan overcenter relationship with respect to blade member 44 causing thebeam spring 140 to bias the blade member 44 in a snap-action movement toa downward condition, shown in dashed outline in FIG. 4, thereby closingcontacts 46 and 48.

The yoke member 134 is shown in solid outline in FIG. 4 in its at-restcondition biased clockwise about notch 136 in a downward positionagainst a stop (not shown) provided in the housing by the action of theend of spring 140. In the actuated condition the yoke member 134 isrotated upwardly to the position shown in dashed outline in FIG. 4; and,the stop surface 142 contacts the leg of the U-shaped end 57 of leverarm 56 which thus acts as a limit stop for clockwise rotation of yoke134.

As the temperature of the refrigerant in the evaporator drops, the fluidin bulb 76, capillary 74 and capsule 72 contracts lowering diaphragm 70to permit the lever arm 60 to pivot clockwise about fulcrum surface 69and lower the lever arm 56 in counterclockwise movement about stationarypivot 58. As the lever arm 56 is lowered, the surface 142 of the yoke134 is pulled downwardly by U-shaped end 57 of arm 56 causing notch 138to lower the left end of beam spring 140 downwardly through theovercenter point of blade 44 which results in the beam spring 140becoming again unstable and the right hand end of the beam spring snapsthe end of arm 44 upwardly against the stop 130 to break the circuitconnection between contacts 46 and 48 thereby opening the switch.

The electrical actuator means for fulcrum means 62 is shown in theactuated or energized condition in FIG. 4 wherein the fulcrum member 64has been moved downwardly to the full extend of its movement with theupper end of slot 65 resting against the surface of the stop peg 66 thusholding fulcrum surface 67 in its lowest position. In this lowestposition, the lever 60 is positioned to cause the lever arm 56 and yoke134 to actuate switch 42 at the lowest level of upper limit temperaturefor the vehicle passenger compartment. In other words, the compressorclutch is energized at a lower temperature corresponding to the "MaximumCool Down" mode of operation.

In the presently preferred practice in the "Maximum Cool Down" mode thethermostat is set to cut in the compressor, or close switch 42 in therange 32 degrees-45 degrees F. (0-8 degrees C.) and cut out or openswitch 42 in the range 25 degrees-32 degrees F. (-6-0 degrees C.). Inthe "Economy" mode, the compressor switch 42 is closed in the range 38degrees-50 degrees F. (3-10 degrees C.) and opened in the range 32degrees-38 degrees F. (0-3 degrees C.).

If the vehicle operator or user wishes to operate the air conditioningsystem in the "Economy" mode of operation, the operator select switch 80is closed thereby energizing the electrical actuator means 78 by causinga flow of electrical current through coil 108 and heating the bimetalstrip 96. Heating causes the strip 96 to flex upwardly in a mannercausing it to increase its amount of bow thereby permitting tab member67 to move upwardly and member 64 moves upwardly until the lower end ofslot 65 rests against the undersurface of stop peg 66. This permits theleft hand end of lever member 60 to move upwardly thereby raising thetab 68 so that movement of the lever arm 60 about fulcrum surface 67 bydiaphragm 70 occurres at a higher temperature. Thus, the switch 42 isnot closed until such higher temperature is reached thereby delaying theenergization of the compressor clutch. This provides the "Economy" modeof operation inasmuch as the compressor is not cycled as often or inother words, does not operate for as long a period of time.

If reverse operation is desired with respect to the operator selectswitch 80, the bimetal member 86 may be reversed such that in theunheated condition it achieves its maximum amount of upward bowing andin the heated condition moves downwardly.

The present invention thus provides a unique and novel method ofoperation of a refrigeration or vehicle air conditioning system whereina remote operator select switch is provided for changing the mode ofoperation of the system. In one position of the operator select switchan electrically energized actuator is de-energized to cause a thermostatsensing evaporator temperature to have a first or lower temperature ofactuation for energizing the compressor. When the operator select switchis moved to a second position, the electrical actuator is energized tocause the thermostat to have a second actuation temperature to changethe temperature limit at which the compressor is energized for coolingof the compartment. In the preferred practice of the invention, thethermostat is a mechanical device employing expanding fluid in apressure capsule connected to a capillary for sensing evaporatortemperature. The expansion of the capsule moves a lever means whichactuates a snap acting switch for energizing the compressor. Theelectrical actuator means for moving the lever means fulcrum comprises aheated bimetal strip which moves a sliding member for changing thefulcrum of the lever means to change the actuation point of the snapacting switch.

The present invention thus permits the operator select switch to belocated remotely from the compressor clutch cycling thermostat to enablethe operator to select either an "Economy" or "Maximum Cool Down" modeof operation. The present invention utilizes a mechanical thermostatwhich may have its actuation temperature changed electrically by remoteactuation of a switch and thus maintains the reliability and lowmanufacturing cost of a mechanical thermostat, yet permits theflexibility and convenience of electrical control of the operation ofthe thermostat.

Although the invention has been described hereinabove with respect tothe illustrated embodiment, it will be understood that the invention iscapable of modification and variation and limited only by the followingclaims.

I claim:
 1. A remotely settable thermostat assembly comprising:(a)mounting structure; (b) switch means disposed on said mountingstructure, including a pair of electrical contacts at least one of whichis movable, said switch means operable upon actuation and deactuation tomake and break said contacts; (c) fulcrum means defining a pivot surfacedisposed on said mounting structure and movable thereon between a firstand second fulcrumming position; (d) lever means disposed on saidmounting structure for pivotal movement on said pivot surface; (e)thermally responsive means including actuator means operative to movesaid lever means for effecting actuation of said switch means at apredetermined temperature; (f) electrically operated means, includingheating means, disposed on said mounting structure operative upon remoteelectrical energization and de-energization to move said fulcrum meansbetween said first and second fulcrumminq positions for providing achange in said switch means actuation temperature.
 2. The thermostatassembly defined in claim 1, wherein said thermally responsive meansincludes a fluid filled bulb and capillary tube having a diaphragmmovable in response to fluid expansion and contraction caused bytemperature changes experienced by the bulb.
 3. The thermostat assemblydefined in claim 1, wherein said switch means includes a snap-actingmechanism.
 4. The thermostat assembly defined in claim 1, wherein saidlever means includes a first member pivoted about a stationary pivot onsaid mounting structure and having a distal portion contacting saidswitch means, and a second member pivoted on said pivot surface with thedistal portion thereof contacting said first member.
 5. The thermostatassembly defined in claim 1, wherein said electrically operated meansincludes a bimetal member and an electrical coil for effecting heatingof said bimetal member.
 6. The thermostat assembly defined in claim 1,wherein said electrically operated means is operable upon energizationto move said fulcrum means to lower said switch actuation temperature bya preselected amount.
 7. The thermostat assembly defined in claim 1,wherein said electrically operated means is operable upon energizationto move said fulcrum means to raise said switch actuation temperature bya preselected amount.
 8. The thermostat assembly defined in claim 1,wherein said fulcrum means comprises generally a member having arelatively thin, flat configuration with a slot formed therein and apost extending from said mounting structure extending into said slotsuch that said post limits sliding movement of said member, with saidpivot surface defined on one end of said member.
 9. The thermostatassembly defined in claim 1, wherein said fulcrumming means includesapertured member with a stop provided on said mounting structure andreceived in said aperture for limiting movement of said member, withsaid pivot surface formed on one end portion of said member and withsaid electrically operated means contacting the end of said memberremote from said one end.
 10. A remotely settable controller assemblycomprising:(a) housing means; (b) switch means mounted on said housingmeans and operable upon actuation and deactuation to open and close aset of contacts adapted for controlling current flow in an electricalcircuit; (c) a fluid pressure capsule mounted on said housing means andhaving an inlet port and including a flexible wall portion operable tomove in response to changes in fluid pressure in said capsule; (d) afulcrum member disposed for movement between a first and second positionon said housing means, said fulcrum member defining thereon a pivotsurface; (e) lever means including a member disposed for pivotedmovement on said pivot surface and contacted by said flexible wallportion, said lever means operable upon movement by said flexible wallportion to effect actuation and deactuation of said switch means; (f)electrically energized means disposed on said housing means andoperable, upon energization to move said fulcrum means between saidfirst and second positions for changing the position of said pivotsurface, wherein said fulcrum surface in said first position is operableto cause said lever means to actuate said switch means at one of alesser or greater fluid pressure in said capsule, and operable in saidsecond position to cause said lever means to actuate said switch meansat the other of said lesser or greater fluid pressure in said capsule.11. The controller defined in claim 10, further comprising a liquidfilled bulb and capillary, with said capillary connected to said capsuleinlet port, said bulb adapted for remote temperature sensing.
 12. Thecontroller assembly defined in claim 10, wherein said electricallyenergized means includes electrical resistance means.